The present invention generally relates to airless dispensing pumps, and more specifically, but not exclusively, concerns an airless dispensing pump that is able to be easily primed in order to efficiently pump viscous fluids while at the same time minimizes contact with sources of contamination, such as air and metals.
Airless type pumps have been developed for a wide range applications including dispensing personal care products, such as skin creams, skin lotions, toothpaste and hair gels, as well as food sauces, and the like. Many such products deteriorate rapidly when placed in contact with air and so it is important to prevent air from entering the package when dispensing the product. In typical dispensing pump applications, air is allowed to enter the container via a venting path in order to equalize the pressure inside the pack as product is dispensed. Were this not the case, the container would progressively collapse or, in the case of rigid containers, the increasing vacuum in the container would exceed the ability of the dispensing pump to draw product out of the container.
With conventional dispensing pumps having a suction pipe or tube, the ability to evacuate the entire contents of the container is relatively poor for viscous products. Usually, the viscous product, such as a cream, is drawn up the suction pipe, which initially works well, but the viscous product does not self-level. As a result, a cavity or hole is formed in the surface of the product to a point where the dispensing pump dispenses only air because it is unable to dispense the product that remains adhered to the sidewalls of the container. As a result, it is common for only about 50% to 60% of the total pack contents of the viscous product to be dispensed with conventional dispensing pumps.
In airless type dispensing systems, there are two common ways to overcome the above-mentioned problems, either by using a collapsible bag type design or by using a follower piston type design. With the collapsible type design, a collapsing bag is attached to the dispensing pump, which progressively collapses as the contents are removed. In the follower piston type design, a rigid container, usually cylindrical or oval in form, has a follower piston that progressively reduces the container volume as product is drawn out by the dispensing pump.
In either type of airless dispensing system, initial priming of the pump mechanism can be somewhat difficult due to the viscous nature of the contents. Even when properly primed, the pump mechanism may not dispense a sufficient amount of fluid due to constrictions within the pumping mechanism, especially the valves. With viscous products, the valves within the pump mechanism need to provide relatively large flow openings, but at the same time, close rapidly to ensure that the product is efficiently pumped. Due to differences in viscosities of various products, it is difficult to easily and inexpensively reconfigure the pumping mechanism to accommodate products with different properties. It is also desirable for a number of products, such as pharmaceuticals, to not come in contact with metal, which can tend to contaminate the pharmaceutical product, and therefore, there is a need to minimize or even eliminate metallic component contact within the pumping mechanism. In typical airless pump designs, after dispensing, product may remain at the outlet of the dispensing head where the product may dry or harden due to contact with air. The dried product usually creates an unsightly appearance, and sometimes can lead to clogging of the outlet. Thus, there is a need for improvement in this field.